Nanedi Vallis

. The origin of this long, winding valley is enigmatic. Some features, such as the terraces and the small stream in its floor (top), suggest that water flowed continuously across the surface for an extended period of time, deeply eroding the rock layers like rivers do on Earth. Such conditions would suggest that liquid water was once stable on Mars, which would have required a denser atmosphere and a higher ground temperature than exists now. Other features, including the dearth of tributaries, suggest that ground collapse could have also contributed to the valley’s formation. Both continual flow and collapse probably played a role in Nanedi’s formation. This image, taken from the Mars Global Surveyor, covers an area of 9.8 kilometers by 18.5 kilometers; the valley is about 2.5 thousand meters wide, while the small stream near the top is just 200 meters wide. Nanedi Vallis is located at 28.4 degrees south and 42.0 degrees west. Nanedi is the word for “planet” in Sesotho, national language of Lesotho, Africa. (Courtesy of NASA, JPL and Malin Space Science Systems.)